Suite spectrale d'Adams et invariants cohomologiques des formes quadratiques

Abstract

For any field k of characteristic 0 the Adams spectral sequence for the sphere spectrum based on Suslin-Voevodsky modulo 2 motivic cohomology [8] converges to the graded ring associated to the filtration of the Grothendieck-Witt ring of quadratic forms over k by powers of the ideal generated by even-dimensional forms. Moreover, some property of the modulo 2 motivic cohomology of k, which is a consequence of Voevodsky 's proof of Milnor's conjecture on modulo 2 Galois cohomology of k [9], implies that the spectral sequence degenerates in the critical area. This allows us to give a new proof of the Milnor conjecture on the graded ring of the Witt ring of k [4] which differs from [11].